Coating system which includes an acrylic lacquer top coat



Oct. 4, 1966 5, PORTER, JR 3,276,905

COATING SYSTEM WHICH INCLUDES AN ACRYLIC LACQUER TOP COAT Filed Oct. 19, 1961 THERMOSET PRIM ER METHYL METHACRYLATE. 2R u1 $r LACQUER TOP COAT ILL I f I H k SUBSTRATE INVENTOR. 54114042 Paw-5R J United States Patent 3,276,905 COATING SYSTEM WHICH INCLUDES AN ACRYLIC LACQUER TOP COAT Samuel Porter, Jr., Tarentum, Pa., assignor to The Pittsburgh Plate Glass Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 19, 1961, Ser. No. 146,271 22 Claims. (Cl. 117-75) This invention relates to coating systems which include acrylic lacquer top coats. More particularly, this invention relates to coating systems comprising a top coat of acrylic lacquer and pigmented or unpigmented primer compositions, containing cellulose acetate butyrate.

The invention further relates to outstanding primer compositions containing an unsaturated carboxylic acid amide interpolymer and cellulose acetate butyrate.

Because methyl methacrylate lacquers composed of homopolymers and copolymers of methyl methacrylate form films having excellent gloss retention over long periods of exposure both outdoors and indoors, their use has become Widespread, particularly in the automotive industry as finish coats for automobiles and other vehicles.

The expanding use of these methyl methacrylate lacquers, however, has given rise to many problems. The biggest problem encountered is the relatively poor adhesion of methyl methacrylate lacquers to metal surfaces, which in turn results in a low level of metal protection and a low level of rust inhibition of the painted metal surface. In order to overcome this shortcoming of methyl methacrylate lacquers, various primers have been developed which act as a bond between the lacquers and the metal surface. In other words, the chief requirement for the primer composition is that it have very good adhesion to both the metal substrate and to the top coat lacquer.

In choosing a suitable composition to be used as a primer, it is quite the exception to find one which will form a good, strong, adhesive bond between the primer and the top coat of methyl methacrylate lacquer composition. By their very nature, methyl methacrylate polymers have poor adhesion because they have no reactive polar groups such as are known to promote adhesion, and must rely primarily on mechanical adhesion.

In many instances, especially in the automotive industry, another composition is used as a surfacer over the primer, both of which are covered by a coat of lacquer. This surfacer composition is usually produced with a high pigment-to-binder ratio on the order of about 45 percent to 50 perecnt by volume of the binder or vehicle. This high pigment-to-binder ratio provides for a composition which may be used to fill any discontinuities in the surface of the substrate and also provides a surface which may be sanded to a smooth and level base for the top coat. Moreover, the sanded surface, because of the minute indentations from the sanding, provides much more surface area for contact between the top coat and the primer-surfacer substrate. It has been found that the sanded or unsanded surfaces of the primer-surfacer composition are far from satisfactory even though the adhesion between the primer-surfacer coating and the top coat is improved because these high pigment-to-binder ratios produce a surface which results in poor hold-ou of the methyl methacrylate lacquer top coat; that is, the gloss of the top coat is decreased by the minute roughness of the surfacer. It is also well known that high pigment-to-binder 3,276,905 Patented Oct. 4, 1966 ratio primer-surfaces lack the required protection against salt water corrosion and also lack flexibility and resistance to chipping when abraded.

It has now been discovered that small amounts (as little as l perecnt by weight based on a total resin solids) of cellulose acetate butyrate promotes adhesion of numerous resinous compositions to materials comprising mainly polymers of methyl methacrylate. Good acrylic adhesion is obtained with as little as from about /2 percent of the solids of cellulose acetate butyrate to about 30 percent by weight cellulose acetate butyrate. The preferred range, however, is from about 3 to about 20 percent by Weight of cellulose acetate butyrate. While pigmentation of the primer composition is desirable, extremely good adhesion is obtained with very little or no pigment.

In accordance with the instant invention the acrylic top coats are superimposed directly over a cured baked resinous composition containing cellulose acetate butyrate, particularly the well-known baked thermoset vehicle containing automotive primer compositions.

Broadly, the present invention includes the use of cellulose acetate butyrate in any resinous composition to improve adhesion to acrylic lacquer type compositions. The invention is particularly concerned with the use of cellulose acetate butyrate to promote acrylic adhesion in curable compositions which may be used as primers for the acrylic lacquer compositions. The expression curable as used in the instant application is intended to include all resins which can be cross-linked through the action of heat with and without the presence of a catalyst; through the action of oxygen from the air with 'or without the aid of heat and/ or a catalyst or drier, or through the presence of a resin having functional groups of suflicient activity to react upon aging with or without a catalyst. Curable resins are also commonly defined as those resins which have their melting point increased by application of progressively higher temperatures.

Preferably the invention is applied to drying oil modified alkyds, rosin modified alkyds, mixed or coreacted alkyds and amino-formaldehyde resins, mixed or coreacted alkyds and epoxy resins, mixed or coreacted alkyds, amino-formaldehyde resins and epoxy resins, mixed or coreacted higher fatty acid esters of epoxy resins with alkyds and/ or amino-formaldehyde resins, mixed or co reacted aldehyde-modified unsaturated carboxylic acid amide interpolymers with any of the above, the thermosetting coreaction products of acid-containing acrylics with amino-formaldehylde resins and the like.

If the solvent system remains simple there is usually no problem with compatibility of the cellulose acetate butyrate with the various resins and resinous blends which are employed as acrylic primers. In many instances, however, good adhesion is obtained even Where there is a slight incompatibility between the primer resin and the cellulose acetate butyrate.

It is also possible to add the cellulose acetate butyrate to emulsified resinous compositions by selecting the proper emulsified cellulose acetate butyrate composition.

Various cellulose acetate butyrates, which may be used in the practice of the instant invention, include those having at least 25 percent of the ester units substituted with the butyral residue. It is preferred, however, that at least 35 percent. of the units be ibutyrate units. The following table sets forth various commercially available cellulose acetate butyrates which may be used with the compositions of the instant invention.

TABLE lI Continued Solution 20% Solution A13- A13- AB- EAB- AB- .AB- AB- AB- EAB- AB 272-3 272-20 381- 381-20 500- 272-3 272-20 38l 381-20 500- 1&2 1&5 1&2 1&5

65--- Benzene-Methanol 4:1 S S S S S S S S S S 66-- Benzene-Methanol 1:l S S S S S S S S S S Aromatic Hydro- 67.-- BenzeneMethanol 1:4 S S S S BSS S S S S BSS carbon-Alcohol 68--. Toluene-Methanol 4:1. S S S S S S S S S BSS Mixtures. 69.-- Toluene-Methanol 1:1- S S S S BSS S S S S BSG 70.-. Toluene-Methanol l:4 S S S BSS IBB S S S BSS IBB B-Borderline solubility, grainy or partly soluble (definite increase in viscosity).

GSemigel, clear gel or white gel. I-Insoluble or swollen.

Where only one letter appears, there is no essential difierence in solubility at different temperatures. Where three letters appear, the first indicates solubility at room temperature, the second at elevated temperatures and the third indicates solubility when cooled back to room temperature.

The coating system of the instant invention is depicted in the accompanying drawing illustrating a metal substrate coated with a primer containing cellulose acetate butyrate and an acrylic lacquer superimposed on the primer.

The primer coat compositions of the instant invention may be employed with any methyl methacrylate type lacquer. The constituents of the lacquer may be varied in kind and/ or in proportion by means which are well known to the art, and those which are set forth in the following description are only representative of a wide variety of such lacquers which may be used in the coating system of the instant invention.

While homopolymers of an alkyl methacrylate, particularly methyl methacrylate or ethyl methacrylate, may be utilized, a particularly useful and preferred group of polymethyl methacrylate copolymers Which may be employed in the preparation of top coat lacquers are copolymers of methyl methacrylate with at least percent by weight of another alkyl ester of an unsaturated carboxylic acid, such as acrylic acid, methacrylic acid, itaconic acid, and the like. The full and detailed description of these resinous compositions is more fully set forth in copending application Serial No. 584,474 filed May 14, 1956, and application Serial No. 108,292 filed May 8, 1961, now US. Patent No. 3,194,777.

The modifying monomer, that is, the alkyl ester of an unsaturated carboxylic acid, is preferably utilized in an amount of about 10 percent to about 30 percent by weight, and the methyl methacrylate, 70 to 90 percent by weight. However, amounts as high as 50 percent by weight of the alkyl ester also may be utilized to give copolymers Which impart the desired characteristics of coating compositions. The exact quantity of the alkyl ester of an unsaturated carboxylic acid employed will depend, of course, on the particular ester utilized; for example, those monomers with the most plasticizing ability, such as ethyl acrylate, butyl acrylate, octyl acrylate, lauryl methacrylate and decyl-octyl methacrylate should be used in smaller amounts. Broadly, the alkyl groups may contain from 2 to 18 carbon atoms; preferably, however, they should contain at least 8 carbon atoms. Lauryl methacrylate is particularly preferred.

The copolymers of methyl methacrylate and alkyl methacrylate in which the alkyl group contains at least 8 carbon atoms should possess a relative viscosity (N,) in the range of 1.150 to 1.260, and preferably 1.180 to 1,250, to function satisfactorily in coating compositions. Relative viscosity (also known as viscosity ratio) is defined as follows:

etliux time of polymer solution in seconds efilux time of solvent solution in seconds etliux time of polymer solution in seconds efllux time of solvent solution in seconds The following is the preparation of a methyl methacrylate copolymer which may be used in the acrylic lacquer top coats of the instant invention.

Example A A bead polymer of methyl methacrylate and lauryl methacrylate was prepared as follows:

A mixture of 1495 parts by weight of water and 5 parts of an acetylated starch (Kofilm No. 50) was heated with agitation to C. until an almost clear solution was obtained. Fifty (50) parts of buffer solution (prepared by admixing 1 part sodium dihydrogen phosphate, 17 parts disodium hydrogen phosphate and parts water) was added. To the resulting mixture was added a mixture of 450 parts methyl methacrylate, 50 parts lauryl methacrylate, 5 parts benzoyl peroxide, and 6.25 parts of tentiary dodecyl mercaptan. The resulting polymerizat-ion mixture was then heated with agitation to 75 C. to 80 C. for 3 hours, after which the mixture was cooled to 30 C., filtered, washed with water and dried at F. for 16 hours. Clear beads of polymer were obtained. When dissolved to a total solids content of 36 percent in toluene, the polymer solution had a Gardner-Holdt viscosity of S.

The following examples relate to the preparation of acrylic lacquer top coats prepared from the above-described interpolymer.

Example B other members of the Bentone series, MPA (Baker Castor Oil Company), and aluminum stearate may be used.

The above ingredients were charged into a Baker- Perkins mill and ground for 20 minutes and .then charged into a pebble mill with more of the same solution of the polymer of Example A (275 parts), Cellosolve acetate 7 (96.7 parts), and methylethyl ketone (99.8 parts) and ground for 16 hours.

Example C A white lacquer was prepared according to the following formulation:

. Parts by weight Pigment paste of Example B 300.0 36.5% solution of the resin of Example A in toluene 395.0 Butyl benzyl phthalate 7.5 Dicyclohexyl phthalate 15.0 12% -6 second'nitrocellulose solution containing 5% ethyl alcohol, 40% toluene and 43% butyl acetate 41.5

Butyl acetate 26.0 Toluene 28.8 Xylene 21.6 Cellulose acetate 8.0 1% DC 200 silicone solution in toluene 0.25

The above ingredients were homogeneously admixed until a desired lacquer consistency was obtained.

The aldehyde-modified unsaturated carboxylic acid amide interpolymer compositions disclosed and claimed in copending application Serial No. 749,583, filed July 21, 1958, now U.S. Patent No. 3,037,963, are particularly compatible with the various cellulose acetate butyrate resins. It has been found that the adhesion of the various acrylic lacquers to primers comprising mainly these resins is extremely good and the coating systems comprising these prirners for acrylic lacquer top coats have all of the qualities which are demanded by the automotive industry.

In the preparation of the aldehyde-modified amide interpolymer resin a polymerizable unsaturated carboxylic acid amide is polymerized with one or more ethylenically unsaturated monomers, and the resulting interpolymer reacted with an aldehyde.

In the event the aldehyde is utilized in the form of a solution inbutanol or other alkanol, etherification will take. place so that at least some of the methylol groups in the above structure will be converted to groups of the structure wherein R. is selected from the class consisting of hydrogen and a saturated lower aliphatic hydrocarbon radical having its free valences on a single carbon atoms, and R is a member of the class consisting of hydrogen and the radical derived by removing the hydroxyl group from the alkanol.

It is desirable that at least about 50 percent of the methylol groups be etherified since compositions having less than about 50 percent of the methylol groups etherified will tend to the unstable and subject to gelation. Butanol is the preferred alcohol for use in the etherification process, although any alcohol, such as methanol,ethanol, propanol, pentanol, octanol, decanol, and other alkanols containing up to about 20 carbon atoms may also be employed as may aromatic alcohols, such as benzyl alcohol or cyclic alcohol.

While either acrylamide or methacrylamide is preferred for use in forming the interpolymer component, any unsaturated carboxylic acid amide can be employed. Such other amides include itaconic acid diamide, alpha-ethyl acrylamide, crotonamide, fumaric acid diamide, maleic acid diamide, and other amides of alpha, beta-ethylenically unsaturated carboxylic acids containing up to about carbon atoms. Maleuric acid, and esters thereof, and imide derivatives such as N-carbamyl maleimide may also be utilized.

Any polymerizable monomeric compound containing at least one CH =C group may be polymerized with the unsaturated carboxylic acid amide. I

It is tobe understood that the above polymerizable olefinic monomers are representative only, and do not include all of the CH =C containing monomers which may be employed.

Preferably, the interpolymer should contain from about 2 percent to about 50 percent by weight of the unsaturated carboxylic acid amide-component, the balance being the other ethylenically unsaturated monomer (s). It has been found that those interpolymers containing the higher levels of the 'amide component with those monomers which ordinarily form hard polymers give hard and flexible films, whereas interpolymers containing lower levels of the amide component with those monomerswhich ordinarily formsoft homopolymers tend to be considerably softer. If more .than one ethylenically unsaturated monomer is polymerized with the amide, the proportions of such additional monomers utilized will depend upon the characteristics which the monomer or monomers will impart to the final interpolymer.

Minor amounts of the ether resins may be blended advantageously with the aldehyde-modified interpolymers of the instant invention. Examples of these other resins include alkyd resins (U.S. Patent 2,940,945), epoxy resins (U.S. Patent 2,870,117), vinyl halidel resins (U.S. Patent 2,870,116) and nitrocellulose (U.S. Patent 2,940,943).

The carboxylic acid amide interpolymer resin prepared according to the disclosures in the above-identified patents is reacted with an aldehyde, preferably in the presence of an alcohol.

Similar polymeric materials may also be obtained by first reacting the amide with an aldehyde, such as formaldehyde, to obtain an alkylolamide, for example, a methylolamide, and then polymerizing the methylolamide with one or more of the ethylenically unsaturated monomeric materials disclosed hereinabove. The polymerization utilizing a methylolamide is carried out in substantially the same manner as when the amide is interpolymerized with one or more monomers.

The polymeric materials may be prepared by still another route; namely, by polymerizing N-alkoxyalkyl amides, for example N-butoxymethyl acrylamide, with one or more of the CH =C monomers set forth hereinabove. This method, described in copending application Serial No. 775,380, filed November 21, 1958, now U.S. Patent No. 3,079,434, does not require reaction of the polymer with an aldehyde since the N-alkoxyalkyl amide monomers already contain R HORr groups, wherein R and R have the meaning set forth above.

In application Serial No. 775,380 there is disclosed also the preparation of the unsaturated carboxylic acid amide interpolymers by emulsion techniques. In accordance with the instant invention, cellulose acetate butyrate may be advantageously blended with the interpolymers prepared in this manner to obtain compositions which when cured as a. film have exceptionally good adhesion to acrylic lacquers.

Where the aforementioned aldehyde-modified carboxylic acid amide interpolymers are to be employed as primers for automotive finishes, it is preferable that low temperature curing compositions be employed because much of employed for low temperature curing of the aldehydemodified amide inter-polymers; and in application Serial No. 677,778, filed August 9, 1957, now US. Patent No. 3,050,495, there is disclosed the various blends of the -10 Example E Example D was repeated substituting succinic anhydride for the maleic anhydride of the example. The reaction was carried out in such a way as to react the suc gi g m Instant mvemlon Wlth melanfine'formalde' cinic anhydride with about 40 percent of the available hydroxyl groups of the allyl alcohol-styrene copolymer. P gg g ifi gg g g g gg i gg g zgiqggzg fi The resulting product had a Gardner-Holdt viscosity of and ed value 41.0. amounts rapgmg from about c621} to about T he r is tiirated ca r lfioxylic acid amides which are cong by wglght thealmmer q g 10 densed with an aldehyde and subsequently ethcrified in gi g g g 1325 3 22 3: gy i gfi as g ssiz: an alcohol are prepared simply by refluxing the amide and the other comonomers in the presence of one of the aforefiiggg g g g ii 3; g i gggfiggg lessen the Iher' mentioned catalysts such as cumene hydroperoxide and a chain transfer agent in an alcoholic solution or in an f In g z to the bF i ;3 ladducts g f' 15 alcoholic hydrocarbon solvent mixture (about to 100 lorma y e z e y 3 0 percent based on the weight of the reactant monomers). lowgr curing empera i f .3 g g ere Sig After about percent to percent of the monomers groupme i 5 2; Sal a 1 e have been converted, formaldehyde in the form of parag fgg 5 5 x 2 gai a fz g z 1 20 formaldehyde or an alkyl Formcel (40 percent butyl alcoto reduce the i tem 525s F P Dye hol solution of formaldehyde) is added with a small The followin i 5 .nustratg in d t n th amount of maleic anhydride. In order to obtain maxition of the Tesingws ii which 2 mum conversion of the reactive monomers it is usually in the resinous primer c mpositions of the instant inv en- Pee-essay to add a catalyst (cu-mega hydropemxlde) durtion These exam 16s are iven b wa of .nustrat.on 25 mg the course of the polymerization (every one or two m b i. g All y d 1 t 1 hours), the reason being that the said catalyst is used up 5y i z l g i g t p g an Percen ages during the reaction. Amounts of about /2 percent to 1 percent based on the monomer SOhdS should be added E l D after each lto 2-hour interval. As previously men- 30 tioned, it has proved advantageous to blend minor The following materials were charged into a vessel amounts (5 to 10 percent by weight) of an epoxy resin equipped with stirrer, condenser and temperature measurwith the said unsaturated carboxylic acid amide intering means: polymer. This may be done by hot or cold blending. Parts by weight The reaction mass is then refluxed with an azeotropic Allyl alcohol-styrene copolymer (Shell X-450) 35 distillation for a substantial length of time (about 3 OH equivalent per grams-0.45; hydroxyl hours) to remove the water of reaction. The following groups per mole5.2 85.3 table sets forth the components of various aldehyde- Maleic anhydride 14,7 modified carboxylic acid amide interpolymers which Methylethyl ketone 33.3 have been prepared by this process.

TABLE III Example No. (Parts by Weight) F G H I I l K L M MATERIALS t 5320"" $5??? tit-"- 38 i232"- 33??" 3'? enP Egll ylacrylate 975.0 6600---- 11.8..... 132.0 Methyl methacrylate 8.8. Acrylonitrile 4.0 Methaerylie acid 37.5--- 67.5 0.6 1.2 7.5 7.5 0.5. Tertiary dodecylmereaptan 22.5 54.0.--" 0.8 0.2 3.75 3.75 0.6. Cumene hydroperoxide 37.5 6.0"--. 0.5 0.4 9.0 9.0 0.5 M1 h d... r s-e----- sa sa -2%. 8810311 1 a -a Epon solution (75% Epo 1001 xy Solvesso Eutanmbikuifis 320 lfigo--- 10.0"-.- 200---- 75.0 75.0-- 10.0.

011 S01 Tgluene 9310---- 1,525.0- 10.0 150.0 1500---. 10.0. Xylene 5.0 75.0

Paornnrrns itiifis-panama 6 t?? 3 9' tit? ii vt i9?? Color (ardnerynu Gma X I: 3-4 3max:: Wt./Gal. (lbs) 8i.1 8.04"--- 8.1=l:.1 Acid value 2 max 6.5-7.5-.. 6-8

1 Eleven (11) parts of Example J were distilled ofi. To this portion was added Bakelite 2002 (1.1 parts), xylene (1.1 parts) and aromatic naptha (Solvesso 150) (10 parts).

The above components were refluxed until the product had an acid value of 60-64 (about 4 to 8 hours). The product was then diluted to 50 percent solids with toluene, the resulting resinous product having the following analysis:

Solids (percent) 50.0 Hydroxyl value 65.0 Acid value 42.0

Viscosity (Gardner-Holdt) E-F 75 Red iron oxide pigment 264 Barytes 1490 Aluminum silicate 1 1 Example N-COntinued Parts-by weight The above ingredients were ground for 16 hours in a steel ball mill.

Example P Parts by weight 2940 Lithopone Lampblack (Molacco black) suspending agent, polyethylene (multipurpose additive, Baker Oil Company) 30 Product of Example F, 320 Solvesso 100 (high boiling aromatic hydrocarbon naphtha) The above ingredients were ground for 16 hours in a steel ball mill. Five hundred (500) parts more of the product F were then added to the steel ball mill as letdown and the ingredients were ground for another hour to effect homogeneity.

Example Q 7 Parts by weight Lithopone 294 Lampblack (Molacco black) 3 .Suspending agent (multipurpose additive, Baker Castor Oil Company) 3 Product of Example I 32 Solvesso 100 (high boiling aromatic hydrocarbon naphtha) 68 The above ingredients were charged into a steel ball mill and ground for 16 hours. Fifteen (15 parts more of the product of Example I were added as letdown and the mixture was ground for another hour to effect homogeniety.

Example R Parts by weight Lithopone 294 Lampblack (Molacco black) 3 Multipurpose additive (Baker Castor Oil Com- P y) 3 Cellosolve acetate 68 Xylene 25 Product of Example L 32 The above ingredients were charged ,intoa steel ball mill and ground for 16 hours. Fifty (50) parts more of the product of Example L were added as letdown and the mixture was ground for another hour to effect homogeneity.

Epoxy ester resinous composition (55% solids in xylene solution, containing 40% low rosin tall oil,

- 5%' dimer acids and 55% Epon 1004, solution acid no. of 7 and Gardner-Holdt viscosity of Q 56 Cellosolve acetate 70 The above ingredients were charged into a steel ball milland ground for 16 hours. One hundred (100) parts more of the alkyd epoxy resin were added as letdown and the mixture was ground for another hour to efiect homogeneity.

Example T Parts by, weight Lampblack pigment (Molacco black) 30 High boiling aromatic solvent (Solvesso 100) 676 Suspending agent (multipurpose additive from Baker Castor Oil Company) 30 Product of Example G 324 Lithopone (70% barium sulfate and 30% zinc sulfide) 2940 The above ingredients were ball milled for 16 hours in a pebble mill after which 500 parts more of the resinous product. of Example G were added as holdout and the mixture was further ground for another half hour to obtain homegen'eity. The resulting paste contained 67 percent pigment and 9.2 percent of the resinous product of Example G.

Example U A pigment paste was made up as follows:

Parts by weight Lithopone (70% barium sulfate and 30% zinc sulfide 294 suspending agent (multipurpose additive from Baker Castor Oil Company) 3 Resinous product'of Example H 32 Lampblack pigment (Molacco black) 3 High boiling aromatic solvent (Solvesso 100) 1 68 The above ingredients were mixed in a mill for 15 minutes, after which 50 parts more of the resinous product of Example F was added as holdout to the said mixture. The mixture was then further ground for 15 minutes to eflect homogeneity of the mixture.

Example V Parts by weight Lampblack pigment (Molacco black) 30 Liffihmone (70% barium sulfate and 30% zinc sule) Suspending agent (multipurpose additive from Baker Castor Oil Company) 3 Alkyd resin, 50% solids (55% glycerol phthalate,

39.1% dehydrated castor oil, 2.4% .paratertiary. butyl benzoic acid and 3.5% glycerol) High boiling aromatic solvent (Solvesso 100) The above ingredients were -mixed in a pebble mill for 16 hours to effect intimate grinding. Resulting paste had 67 percent pigment and 10 percent of the alkyd resin.

Example W V Parts by weight Barytes 835.0 Lithopone 288.0 Lampblack pigment (Molacco bla'ck) 28.8 Product of Example K 120.0 Cellosolve acetate 263.0

The above ingredients were charged into a steel ball mill and ground for 24 hours. One hundred forty-three and two-tenths 143.2) parts more of the product of Example K were added as washout and the mixture was ground for another hour to effect homogeneity.

The compositions of the following Table IV were adjusted toa suitable viscosity and sprayed on phosphatized steel panels (Bondferite in sufficient amounts to produce a smooth, dry, uniform coating; about 1.2 mils thick. The panels were then baked at a temperature of about 275 F. for 45 minutes. The compositions of Examples X through XIV were baked at 350 F. for 20 minutes. The coated panels were then cooled, sprayed with two different acrylic lacquers (Duracryl and Lucite) and baked to a film thickness of about 2 mils at 225 F. for 30 minutes. All of the panels manifested excellent acrylic adhesion, excellent mandrel bend and excellent cold bend. The acrylic adhesion was tested by three different methods; the crosshatch method, the knife method, and the tape method.

The crosshatch method comprises cutting a series of parallel lines about A inch apart in the coating surf-ace and another series of parallel lines over the same area but perpendicular to the first set of parallel lines. The amount of chipping observed is a measure of the adhe- The knife method comprises gouging a groove into the surface of the coating with the flat tip of the knife and observing the manner in which the coating is removed. If the adhesion is poor, the coating will break The tape method comprises cutting an X in the surface of the coating with a knife, adhering a pressuresensitive tape against the X surface and removing the said tape in a rapid motion almost parallel to the plane of the surface. The amount of coating which comes oil with the tape is also a measure of the adhesion of the coatmg.

The mandrel bend test comprises placing the coated panel on a standard conical mandrel and rolling and bending the said panel intimately around the cone. If the adhesion is poor the coating will peel from the tapered end of the cone.

The cold bend test comprises bending the coated panel around a cylindrical mandrel at temperatures below freezing F.) wherein both the mandrel and the panel have been .maintained below freezing for at least an hour.

The adhesion of acrylic lacquers to primers made from the compostion of Table IV without the use of any cellulose acetate butyrate is extremely poor and in many infreely away from the substrate.

20 stances nonexistent.

TABLE IV AldehydeModified Un- Adduct of a 7 Exsaturated Carhoxylic Acid Dicarboxylic Acid Pigment Paste Cellulose Acetate Butyrate Solvent Parts by Other Materials ample Amide Parts by Weight and Hydroxyl-Con- Parts by Weight Parts by Weight Weight Parts by Weight taining Polymer Parts by Weight I Product of Ex. F, 10% ac- Product of Ex. D, Product of Ex. 20% sec. CAB 1 solution Cellosolve acerylamide, 25% styrene, Maleic anyd- 374. in 7 :2:1 xylene, butanol, tate, 74.

65% acrylamide, +5% dride adduct of methylethyl ketone mix- Epou 1001; 72. a styreneallyl ture; 30.

alcohol copolymer, 50.

II Product of Ex. G, 15% ac- Product of Ex. Product of Ex. 20% sec. CAB solution in Methyl isobutyl rylamide, 39% styrene, S 374. 1:1 methyl isobutyl keketone, 70;

44% ethyl acrylate, 2% tone, mixture toluene; 50. xylene, 94. methacrylic acid; 72.

HI Product of Ex. H, 15% acdo Product of Ex. 20% sec. CAB solution in Methyl isobntyl rylamide, 82.5% styrene, N 416. xylene. butanol, methylketone, 70.

2.5% methacrylate; 66. ethyl ketone 75. High boiling aromatic hydrocarbon solvent (Solvesso 100) 67.

IV Product of Ex. I, acdo .do Cellosolve acetate rylamide, 20% acryloni- 55. trile, 67.5% styrene, 2.5%. methacrylic acid; 150.

V Product of Ex. J, 10% ac- Product of Ex. 20% sec. CAB Solution Cellosolve acetate, Melamine-formalrylamide, 59% ethyl acry- Q 374. in 712:1 xylene, butanol, 60. Methyl dehyde resin, 20. late, 25% styrene, 6% methylethyl ketone mixisohutyl ketone, methacrylic acid. 1 ture; 50. 54.

VI Product of Ex. K, 10% ac- Product of Ex. D, Product of Ex. )4 sec. CAB (15.6 parts) Cellosolve acetate, Paraplex (3-60,

rylamide, 43.5% styrene, 30. W, 362. solution in Cellosolve ace- 15. Diacetone 10.0.

44% ethyl acrylate, 2.5% tate (15.3 parts) and tolalcohol, 30. Telmethacrylic acid; 83. uene (69.2 parts), 25. uene, 30.

VII Product of Ex. L, 10% ac- Product of Ex. D, Product of Ex. 20% sec. CAB solution Cellosolve acetate, Do.

rylamide, 87.5% styrene, 2 394. in 7 22:1 xylene, butanol, 70. Xylene, 34.

2.5% methacrylic acid; 72. lzuethgethyl ketone mixure,

VIII Product of Ex. M., ac- Product of Ex. D, solution in Oellosolve Paraplex G-60,

rylamide, 38.5% styrene, 5. acetate toluene, 5. 15.0.

44% methyl methacryllatei, methacrylic aci IX Product of Ex. K, 10% ac- Product of Ex. D Product of Ex. sec. CAB (15.6 parts) Diacetone alcohol, Paraplex G-60,

rylamide, 43.5% styrene, 59.9. W, 722 solution in Cellosolve 89. Toluene, 20.5.

44% ethyl acrylate, 2.5% acetate (15.3 parts) and 60. methacrylic acid; 165.5. toluene (69.2 parts), 50.

X Product of Ex. K, 10% ac- 20% sec. CAB solution Oellosolve acetate, Paraplex G-60,

rylamide, 43.5% styrene in 7 22:1 xylene, butanol, 70. Toluene, 10.0.

44% ethyl acrylate, 2.5 o methylethyl ketone mix- 69. methacrylic acid; 170. ture; 25.

XI Product of Ex. K, 10% 20% CAB (EAB 381-2) Cellosolve acetate Paraplex G-60, 10.

aerylamide, 43.5% styrene, solution in 7 :221 xylene, 70. Toluene, 44% ethyl acrylate, 2.5% butanol, methylethyl 69. methacrylic acid, 170. ketone mixture; 25.

XII Product of Ex. K, 16% 15% CAB (EAB 500-1) do Do.

acrylamide, 43.5% styrene, solution in acetone, 33.

44% ethyl acrylate, 2.5% methacrylic acid; 170.

XIII Product of Ex. K, 10% 20% CAB (EAB 500-5) do Do.

acrylamide, 43.5% styrene, solution in 7:2:1 xylene, 44% ethyl acrylate, 2.5% butanol, methylethyl rnethacrylic acid; 170. ketone mixture; 25.

XIV Product of Ex. F, 10% sec. Cellulose acetate acrylamide, 25% styrene, butyrate, 5 (solids). acrylamide, 5%

Epon 1001; 190.

XV- Product of Ex. G, 15% sec. Cellulose acetate acrylamide, 39% styrene, butyrate, 20 (solids). 44% ethyl acrylate, 2%

' methaorylic acid; 160.

XV I Product of Ex. J, 10% )4 sec Cellulose acetate acrylamide, 59% ethyl butyrate, 10 (solids). acrylate, 25% styrene, 6% methacrylic acid; 90.

CAB-Cellulose acetate butyrate.

The adhesion of the various epoxy-resins to various acrylic lacquers is also promoted by the presence of similar amounts of cellulose acetate butyrate therewith.

The epoxide resin which is utilized in the primer compositions of this invention may vary considerably in chemical structure. These materials, which are ordinarily polyglycidyl ethers of bisphenols, or polyethe'r derivatives of polyhydric phenols containing epoxide groups, are formed by the reaction of bisphenols with epichlorohydrin, and range from viscous liquids to hard, brittle resins.

The epoxy resins may advantageously be reacted with monocarboxylic acids, particularly the fatty acids such as those obtained from linseed oil, soya oil, safllower oil, perilla oil, tung oil, oiticica oil, poppyseed oil, sunflower oil, tall oil, Walnut oil, dehydrated castor oil, herring oil, menhaden oil, sardine oil, and the like. The epoxy resins may be esterified simply -'by refluxing the epoxy resin in the presence of one or more of the carboxylic acids while simultaneously removing water azeotropically.

In addition to the epoxy resins which are prepared with a polyhydric phenol and a chloroepoxy compound, the epoxidized ring compounds such as disclosed in US. Patent 2,716,123 may also be used. Union Carbides EP-201 is an example of the commercially available epoxidized ring compounds.

A representative epoxy resin structure may be illustrated as follows: I

invention. The liquid 'epoxide resins normally possess epoxide equivalents (grams of resin containing one gram equivalent of epoxide) below about 300. The liquid resins ordinarily will be of an average molecular weight below 500 and preferably in the range of about 350 to 450. While the liquid resins are much preferred, the solid resins can also be utilized, although compatibility problems are sometimes encountered, making production of the primer considerably more diflicult than is the case with the liquid epoxide resins.

It has been found that where adhesion between the vanous epoxy primers such-as those set forth in US. Patent 2,847,323 is good, it can still be enhanced by the presence of small amounts of the various cellulose acetate butyrates.

The various polyester resins and alkyd resins may also be blended advantageously with cellulose acetate butyrate to promote adhesion to acrylic lacquers in accordance with the. instant invention. These include the various reaction products of the dicarboxylic acids and anhydrides and various polyols with and without long chain fatty acid esters. Particular acids and anhydrides which may be used with the instant invention are phthalic acid, maleic acid, fumaric acid, succinic acid, adipic acid, tetrahydrophthalic acid, hexahydrophthalic acid, terphthalic acid, and isophthalic acid. Among thepolyols (alcohols) which may be employed in preparing the polyester and alkyd resins of the instant invention are included glycerine,

In the foregoing structure, n is a number of a magnitude dependent upon the degree to which the etherification is carried. The most simple epoxy resin will be free of functional groups other than epoxide and hydroxyl groups, and will contain at least 4 carbon atoms, as illustrated by 1,2-epoxy-3,4-epoxy butane. More complex epoxy resins, such as those which result from the reaction of two or more moles of a diepoxide with one mole of a dihydric phenol, or from the reaction of three or more moles of a diepoxide with one mole of a tn'hydric phenol, and diepoxides or polyepoxides derived by polyhydric alcohols such as sorbitol, pentaerythritol, or polyallyl alcohols, may also be used. Among the many phenolic compounds utilized in the preparation of epoxy resins are included the following:

Bis (4-hydroxy-phenyl 2,2-prop ane 4,4'-Dihydroxybenzophenone Bis(4-hydroxy-phenyl) 1,1-ethane Bis (4-hydroxy-phenyl) 1,1-isobutane Bis 4-hydroxy-phenyl) 2,2-butane Bis (4-hydroxy-phenyl) 2,2-propane Bis (4-hydroxy-tertiary butyl phenyl) 2,2-propane 1 Bis 2-hydroxy-naphthyl) methane 1,5 -Dihydroxy-naphthalene The epoxy component of the epoxy resins may be selected from compounds of the following group:

1-Chloro-2,3-epoxy propane (epichlorohydrin) 1-Chloro-2,3-epoxy butane 1-Chloro-3,4-epoxy butane 2-Chloro -3,4-epoxy butane 1-Chloro-2-methyl-2,3-epoxy butane l-Bromo-2,3-epoxy pentane 2-Chloromethyl-1,2-epoxy butane 1-Bromo-4-methyl-3,4-epoxy pentane 1-Bromo-4-ethyl-2,3-epoxy pentane 4-Chloro-2-methyl-2,3-epoxy pentane 1-Chloro-2,3-epoxy octane 1-Chloro-2-methyl-2,3-epoxy octane 1-Chloro-2,3-epoxy decane Those epoxide resins which are liquids are particularly pentaerythritol, sorbitol, mannitol, ethylene glycol, diethylene glycol, propylene glycol, 2,3-butylene glycol and the like. All of the alkyd resins such as short oil modified resins, medium oil modified resins and long oil modified resins may also be blended with cellulose acetate butyrate to improve their adhesion to acrylic lacquers. Various oils which may be used to modify the alkyd resins include linseed oil, soya oil, safilower oil, perilla oil, tung oil, oiticica oil, poppyseed oil, sunflower oil, tall oil,

' walnut oil, dehydrated castor oil (DCO), herring oil,

menhaden oil, sardine oil, and the like.

The various styrene-modified alpha, beta-ethylenically unsaturated dicarboxylic acid alkyds, particularly the maleic acid type, may be blended with minor amounts of cellulose acetate butyrate and subsequently castor laminated into various forms. These castings have good adhesion'to acrylic lacquers.

Adhesion between acrylic lacquers and the various amino-formaldehyde resins such as urea-formaldehyde and melamine-formaldehyde resins is also promoted by the presence. of minor amounts of cellulose acetatebutyrate. The fast-curing melamine-formaldehyde resins which are employed in acrylic lacquer primers for the automotive industry are particularly adaptable forblending with cellulose acetate butyrate. These fast-curing melamineformaldehyde resins are characterized by melamine which has been methylolated to a limited degree (about.3 to

4 methylol groups per melamine molecule) and further etherified with an alkanol such as butanolto the minimum degree necessary to improve its solubility in the various hydrocarbon solvents and hydrocarbon polar solvent blends.

While it is preferred thatfast-curing melamine-formaldehyde resins be employed, the cellulose acetate butyrate may also be advantageously blended with melamine-formaldehyde resins which are derived from hexamethoxy melamine where the maximum of methylolation and etheriflcation has taken place on the melamine molecule.

Where the urea-formaldehyde resins are employed, cellulose acetate butyrate may :be advantageously blended with both the low-curing and fast-curing urea-formaldehyde resins. The ability of the urea-formaldehyde resins .06 1? is Controlled in the same manner as that which is used to control the curing of the melamine-formaldehyde resins.

The various thermosetting compositions which are prepared from blends of acid-containing vinyl resins or halidecontaining vinyl resins with melamine-formaldehyde or urea-formaldehyde resins may also be blended advantageously with cellulose acetate butyrate. Examples of these compositions which may be found commercially are Rohm and Haas AT-SO and AT-51.

The blends of the above-described epoxy, polyester, alkyd and amino-formaldehyde resins with the aforementioned unsaturated carboxylic acid amide interpolymers may be effectively modified with cellulose acetate butyrate to improve their acrylic adhesion. Moreover, blends of the thermoplastic acrylic polymers with the said interpolymers may be utilized with cellulose acetate butyrate.

The following examples relate to the preparation of epoxy resin primers, epoxy-alkyd resin primers, epoxy and melamine-formaldehyde resin primers.

The above ingredients were charged into a pebble mill and ground for 20 hours (Hegman 7). Then 81.1 parts of 45% solution in hydrogenated naphtha (Union 30 or -Solvesso 2) of an alkyd resin comprising 21.25% soya oil, 21.25% tung oil, 56.7% glycerol phthalate, 0.8% excess glycerine (Gardner-Holdt viscosity U-V, acid No. 19) and ground for /2 hour, and thinned in the mill.

The following ingredients were then added to the reaction mixture:

Parts by weight 26.7

Xylene Hansol (high boiling aromatic .petroleum, boiling :point 140 C.185 C.) 50.5 Epoxy ester solution (60% solids in xylene-32% fractionated cottonseed acid, iodine value of 132 minimum, 68% Epon 1004acid No. 6, Gardner-Holdt viscosity Z) 39.4

The ingredients were ground for another hour and the following were added:

Parts by weight Alkyd resin solution (45 solids in hydrogenated naphtha solventsolids, 21.25% soya oil, 21.25% tung oil, 56.7% glycerol phthalate, 0.8% excess glycerine-Union 30 or Solvesso 2, acid No. 19 and Gardner-Holdt viscosity U-V) 271.3 Phenol formaldehyde resin 16.4 High naphtha tolerance alkylated urea-formaldehydesolution (60% solids in 1:4 xylene-butanol mixture, high naphthal tolerance grns. in 36- 40 ml. aliphatic hydrocarbon naphtha) 18.0 Naphthenate mixture (containing 10.5% Pb, .66%

Co and .67% Mn in aliphatic hydrocarbon) 3.5 Cobalt naphthenate (4%) 5.5 Manganese naphthenate (6% aliphatic hydrocarbon) 1.1 Cresylic acid 3.6 Hansol (aromatic petroleum, boiling point 140- 185 C.) Enjay2 18 Example Y Parts by weight Esterified epoxy resin [55% solids in xylene solvent (solution acid No. 7, Gardner-Holdt viscosity V-W), 40% low rosin tall oil acids, 5% dimer acids 55% Epon 1004] -3 111 Aliphatic hydrocarbon solvent 106 Mineral spirits 60 Barium sulfate (bleached barytes) 196 Hydrite clay aluminum silicate 62 Zinc oxide 13 Zinc potassium chromate (ZnKCrO 42 lecithin solution 4 Anti-settling agent (Troykyd) 2 *Dimer acids are dimerlzed reaction products of linoleic and oleic acid in the presence of steam; iodine value is in the range of from -95.

The above ingredients were charged into a suitable vessel and ground 14 hours. It was ground for 24 hours (Hegrnan 6.9). Forty six (46) more parts of the above esterified epoxy resin were added and ground /2 hour, another 47 parts of the esterified epoxy resin were added and ground another /2 hour. The mixture was thinned and to the reaction mass was added the following ingredients:

Parts by'weight Pigment paste prepared above 739 Esterified epoxy resin [55% solids in xylene solvent (acid No. 7, Gardner-Holdt viscosity V-W), 40% low rosin tall oil acids, 5% dimer acids, 55%

Epon 1004] 103 Resimene 875 (melamine-formaldehyde, fast-curing) 8 Cresylic acid 1 Manganese drier l /z Butyl Cellosolve '14 Hydrocarbon solvent (Enjay 89 Aliphatic hydrocarbon, boiling point 160-205 (Shell Ts 2s 73 The resulting composition had a solids content of 53% and a viscosity (77 F. sec.) of 45,

Example Z Parts by weight The above ingredients were ground for 20 hours to Hegman 7 and an additional 72.8 parts of the same alkyd resin were added. This was then mixed for 1 hour and blended with the following ingredients:

Parts by weight Alkyd resin [50% solids in xylene, solids: 39.1% glycerol ester of dehydrated "castor'oil, 2.4% glycerolester of p-tertiary butyl benzoic acid,

55% glycerol phthalate, 3.5% excess glycerine] 132.2 Castor oil alkyd (60% solids in xylene) 68.0 Epoxy ester [60% solids in xylene (32% fractionated cottonseed acid, iodine value of 132 minimum, 68% Epon'1004), acid No. 6, Gardner- Holdt viscosity Z] 72.8 Urea-formaldehyde resin [60% solids in 20% xylene, 80% butanol, high naphtha tolerance,

gm. in 36-40 ml. of naphtha aliphatic hydrocarbon] 30.1 Iron naphthenate (6% iron in mineral spirits) 4.8 Diethylene diamine 2.0 Butyl alcohol 25.3 Butyl Cellosolve 23.2 Velsicol 45 69.9 Xylene 48.8

It has been found that minor amounts of cellulose acetate butyrate also promote adhesion between acrylic lacquer top coats and certain compositions which were not intended to be used as primers for acrylic lacquers. For instance, water-base resins such as those prepared from adducts of a dicarboxylic anhydride and a drying oil may be employed as a'primer for acrylic lacquers through addition of cellulose acetate butyrate.

The adducts are prepared by reacting a drying oil, a semidrying oil or a long oil alkyd with an unsaturated dicarboxylic acid or anhydride to form water soluble resins.- Generally, the drying oils are those oils which have an iodine value above about 130, and the semidrying oils are those which have an iodine value of about 90 to 130 as determined by method ASTM-D 1467-57T. Included among these oils are linseed oil, soya oil, safflower oil, perilla oil, tung oil, oiticica oil, poppyseed oil, sunflower oil, menhaden oil, sardine oil, and the like. Also included among such oils are those in which the oils per se are modified with other-acids such as phthalic acid (or anhydride) or benzoic acid by first forming a dior monoglyceride or a mixture thereof by alcoholysis, followed by esterification. Polyols other than glycerol can also be employed in the alcoholysis. Other esters of unsaturated fatty acids; for example, those prepared by the esterification of tall oil fatty acids with polyols are also useful. In addition, long oil alkyds having low by droxyl value (greater than 70 percent oil length) using the oils mentioned above are also useful. All of these materials can be reacted with unsaturated dicarboxylic acid anhydrides to give adducts useful in preparing the compositions of this invention. Preparation of these compositions is set forth in detail in copending application Serial No. 815,789 filed May 26, 1959. A typical prepparts of water.

aration of these materials is set' forth in the following example.

Example 22 Thirty and four-tenths (30.4) parts (76 percent) of linseed oil and 9.6 parts (24 percent) of maleic anhydride were placed in a reactor and heated to a temperature of 375 F. The-heat was then turned off and since the reaction was strongly exothermic, the temperature rose to 475 F. After approximately 2 /2 hours, the reaction mixture was added with stirring to a mixture of 10.5 parts of 28 percent aqueous ammonium hydroxide and 1.88 parts of 2-methyl-2-amino-1,3-propanediol and 49.5 The composition had a U-X viscosity on the Gardner-Holdt scale and a solids content of 43 percent. The Gardner Color was 14-16 and the weight per gallon 8.7 pounds. The pH of the composition 1was 8.5. A sample of the resin formed a clear solution in water at a pH of 7.5 without the use of water soluble. organic solvents.

In. order to efiectively blend cellulose acetate butyrate with a water base composition'such as that prepared in the above example,'the following cellulose acetate butyrate emulsion may be prepared:

The above solutions were blended in a Cowles dissolver until a creamy emulsion was obtained.

The following table sets forth compositions which were adjusted to a suitable viscosity and sprayed on phosphatized steel panels (Bonderite' 100) in suflicient amounts to produce a smooth, dry, uniform coating (about 1.2 mils). The panels were baked for 20 minutes at 350 F.) cooled and sprayed with two different lacquers (Duracryl L707 and Lucite) to a film thickness of about 2 mils. However, the panels made from the alkyd resin and the Rohm and Haas AT-51 vinyl type resinswere baked at 275 F. for 45 minutes and 300 F. for 30 minutes respectively. They were then baked for 30 minutes. at 225 F. The adhesion of the coating system was then tested by the previously described crosshatch method, knife method and tape method. In each instance adhesion between the top coat and the primer was much better than for corresponding systems which were prepared using primer compositions not. containing cellulose acetate butyrate.

TABLE V Parts by Parts Ex. Resin Weight Cellulose Cellulose Acetate Butyrate Solvent Number Resin Acetate Butyrate XVII Product of Ex. X (Epoxy ester'alkyd resin and 100 25 10% sec. CAB in 7:2:1 methyl iso- Methyl isobutyl urea-formaldehyde resin vehicle). Eutyl ketoue, butanol, xylene mixetone, 20.

ure. XVIII Product of Ex. Y (Epoxy ester-melamine-formal- 100 25 do D dehyde resin vehicle). XIX Product of Ex. Z (Epoxy ester'alkyd resin and 100 25 do Do.

urea-formaldehyde vehicle). XX Alkyd resin solids in toluene comprising 51.1 1 l 20 do parts glycerol ester of castor oil, 46 parts glycerol phthalate, excess glycerine 2.9 parts). XXI Product of Ex. ZZ 8% Cellulose acetate butyrate emulsion of Ex. ZZZ. XXII"--- Blend of 65 parts of product of Ex. K+25 parts 90 25 20% 54 sec. CAB in 7:221 methyl isoalkyd+l0 parts of product of Ex. A. :mtyl ketone, butanol, xylene mixure. XXIIL Thermoset vinyl resin (Rohm & Haas AT-51)- 90 50 do Blend of 40 parts of product of Ex. K+60 parts of 1 8 cell l tat product of Ex. A. 20. XXV Blend of 45 parts (solids) of product of Ex. K 45 1 3 parts (solids) interpoly'mer of 64 percent methyl methacrylate, 30 percent dibutyl itaconate and 6 percent methacrylic acid.

1 Solids.

Although specific examples have been set forth hereinabove, it is not intended that the invention be limited solely thereto, but to include all of the variations and modifications falling within the scope of the appended claims.

I claim:

1. A metal article having a hard, adherent, crack-resistant coating comprising a layer of primer and a superimposed layer of a polymer of an alkyl methacrylate, said primer comprising (1) a heat hardenable resinous composition comprising an inter-polymer containing from about 2 to 50 percent by weight of an unsaturated carboxylic acid amide in polymerized form based on the total weight of said interpoly-mer and being characterized by having at least one hydrogen atom of an amido nitrogen replaced by the structure:

wherein R is a member selected from the group consisting of hydrogen and lower alkyl and R is a member selected from the group consisting of hydrogen, lower alkyl and alkoxyethyl and (2) cellulose acetate butyrate.

2. The article of claim 1 in which said alkyl methacrylate is methyl methacrylate.

3. The article of claim 1 in which said primer contains an acrylic resin as an additional component.

4. A multiple layer coating system comprising a substrate, a layer of primer and a superimposed adherent layer of a lacquer comprising as the sole methacrylate polymer a polymer selected from the group consisting of homopolymers of an alkyl methacrylate, and copolymers of an alkyl methacrylate with to 30 percent by weight of another alkyl ester of an unsaturated carboxylic acid, said primer being a layer of a coating composition comprising an epoxy resin and cellulose acetate butyrate.

5. The coating system of claim 4 wherein the said epoxy resin is the reaction product of epichlorohydrin and para, para'-isopropylidine diphenol.

6. The coating system of claim 4 wherein the epoxy resin has been esterified.

7. The coating system of claim 6 wherein the said esterified epoxy resin has been esterified with a long chain fatty acid.

8. A multiple layer coating system comprising a substrate, a layer of primer and a superimposed adherent layer of a lacquer comprising as the sole methacrylate polymer a polymer selected from the group consisting of homopolymers of an alkyl methacrylate, and copolymers of an alkyl methacrylate with 10 to 30 percent by weight of another alkyl ester of an unsaturated carboxylic acid, said primer being a layer of a coating composition comprising an alkyd resin and cellulose acetate butyrate.

9. The coating system of claim 8 wherein the alkyd resin is the reaction product of glycerine, dehydrated castor oil, phthalic acid and para-tertiary #butyl benzoic acid.

10. The coating system of claim 8 wherein the alkyd resin is the reaction product of soya oil, tung oil, glycerine and phthalic acid.

11. A multiple layer coating system comprising a substrate, a layer of primer and a superimposed adherent layer of a methyl methacrylate lacquer in which the sole methacrylate polymer is selected from the group consisting of poly (methyl methacrylate) and copolymers of methyl methacrylate with 10 to 30 percent by weight of another alkyl ester of an unsaturated carboxylic acid, said primer being a layer of a coating composition comprising an amino-formaldehyde resin and cellulose acetate butyrate.

12. The coating system of claim 11 wherein the aminoformaldehyde resin is melamine-formaldehyde resin.

13. The coating system of claim 11 wherein the aminoformaldehyde resin is urea-formaldehyde resin.

14. A multiple layer coating system comprising a substrate, a layer of primer and a superimposed adherent layer of methyl methacrylate lacquer in which the sole methacrylate polymer is selected from the group consisting of poly (methyl methacrylate) and copolymers of methyl methacrylate with 10 to 30 percent by weight of another alkyl ester of an unsaturated carboxylic acid, said primer 'being a layer of a coating composition comprising the resin of a reaction product of an unsaturated carboxylic acid containing vinyl resin and an amino-formaldehyde resin and cellulose acetate butyrate.

15. A multiple layer coating system comprising a substrate, a layer of primer and a superimposed adherent layer of methyl methacrylate lacquer in which the sole methacrylate polymer is selected from the group consisting of poly (methyl methacrylate) and copolymers of methyl methacrylate with 10 to 30 percent by weight of another alkyl ester of an unsaturated carboxylic acid, said primer being a layer of a coating composition comprising the adduct of a member selected from the group consisting of an unsaturated dicarboxylic acid and anhydride and a member selected from the group consisting of drying oils, semidrying oils and long oil alkyd resins and cellulose acetate butyrate.

16. The coating system of claim 15 wherein the said adduct is an adduct of maleic anhydride and linseed oil.

17. The coating system of claim 3 wherein the acrylic resin is a copolymer of methyl methacrylate and lauryl methacrylate and the said interpolymer is an interpolymer of acrylamide, styrene, ethyl acrylate and methacrylic acid.

18. The coating system of claim 3 wherein the acrylic resin is a copolymer of methyl methacrylate, dibutyl itaconate and methacrylic acid and the said interpolyrne-r is an interpolymer of acrylamide, styrene, ethyl acrylate and methacrylic acid.

19. The article of claim 1 in which the primer contains an alkyd resin as an additional component.

20. The article of claim 1 in which said primer contains an alkyd resin and an epoxy resin as additional components.

21. A multiple layer coating system comprising a substrate, a layer of primer and a superimposed adherent layer of methyl methacrylate lacquer in which the sole methacrylate polymer is selected from the group consisting of poly (methyl methacrylate) and copolymers of methyl methacrylate with 10 to 30 percent by weight of another alkyl ester or an unsaturated carboxylic acid, said primer being a layer of a coating composition comprising a blend of an epoxy resin, a melamine-formaldehyde resin and cellulose acetate butyrate.

22. A multiple layer coating system comprising a substrate, a layer of primer and a superimposed adherent layer of methyl methacrylate lacquer in which the sole methacrylate polymer is selected from the group consisting of poly (methyl methacrylate) and copolymers of methyl methacrylate with '10 to 30 percent by weight of another alkyl ester of an unsaturated carboxylic acid, said primer being a layer of a coating composition comprising a blend of an epoxy ester resin, a melamineformaldehyde resin, alkyd resin and cellulose acetate butyrate.

References Cited by the Examiner UNITED STATES PATENTS 2,782,131 2/1957 Johnson ll775 X 2,864,722 12/1958 Millar et al 1l772 2,866,720 12/1958 Martin et al 1l7-72 (Other references on following page) '23 UNITED STATES PATENTS Barrett et a1. 117-75 Blake 117-75 X Souder et a1. 117-75 Greif 117-75 Berge 117-75 Sanderson 260-17 Coover 260-17 Levine 117-75 24 OTHER REFERENCES Paist: Cellulosics, Reinhold, New York, 1958, pp. 164- 166 'IP986A2P33.C.3.

5 ALFRED L. LEAVITT, Primary Examiner.

RICHARD D. NEVIUS, MURRAY KATZ, Examiners.

R. S. KENDALL, J. P. MCINTOSH, W. L. SOFFIAN,

Assistant Examiners. 

1. A METAL ARTICLE HAVING A HARD, ADHERENT, CRACK-RESISTANT COATING COMPRISING A LAYER OF PRIMER AND A SUPERIMPOSED LAYER OF A POLYMER OF AN ALKYL METHACRYLATE, SAID PRIMER COMPRISING (1) A HEAT HARDENABLE RESINOUS COMPOSITION COMPRISING AN INTERPOLYMER CONTAINING FROM ABOUT 2 TO 50 PERCENT BY WEIGHT OF AN UNSATURATED CARBOXYLIC ACID AMIDE IN POLYMERIZED FROM BASED ON THE TOTAL WEIGHT OF SAID INTERPOLYMER AND BEING CHARACTERIZED BY HAVING AT LEAST ONE HYDROGEN ATOM OF AN AMIDO NITROGEN REPLACED BY THE STRUCTURE: 